Lake be­com­ing ‘un­fish­able’

Central Otago Mirror - - YOUR PAPER, YOUR PLACE - JO MCKEN­ZIE-MCLEAN

An ex­pe­ri­enced fish­ing guide fears Lake Wakatipu could end up ‘‘un­fish­able’’ with the in­va­sive spread of the al­gae bloom, lake snow, and warns Lake Dun­stan could be next.

Queen­stown fish­ing guide Stu Dever, armed with his rod and reel, voiced his con­cerns about the pres­ence of lake snow in Lake Wakatipu to Otago Fish and Game com­mit­tee mem­bers at a meet­ing in Cromwell on Thurs­day.

His rod was clogged with the thick glob­ules of al­gae after only one day’s fish­ing on the lake.

‘‘That rod, I only used once for one fish­ing trip and got that buildup from lake snow - the prob­lem is very bad. It has got to the stage if you don’t clean your reel you can’t wind it in it gets that thick.’’

The mu­cous-like sub­stance pro­duced by the al­gae cy­clotella has now been ob­served in three South Is­land lakes. In May, slime taken from Lake Wakatipu was con­firmed as lake snow. The al­gae was also found on a fish­ing line at Lake Co­leridge in 2015, after ini­tially be­ing dis­cov­ered in Lake Wanaka in 2004.

Dever said he first no­ticed the thick glob­ules of al­gae in Lake Wakatipu in April and it had got pro­gres­sively worse.

‘‘It is on the top but it’s also down deep and right through vari- ous lev­els. I have no idea how it got into the lake but if noth­ing is done about it, I don’t know where it could end up. The lake could be to­tally un­fish­able.’’

He warned the spread would flow-on to Lake Dun­stan, in Cromwell.

‘‘It will flow on to Lake Dun­stan - our lake drains into Cromwell from the Kawa­rau River...Some­thing has to be done now, ur­gently...

‘‘The al­gae also blocks boat fil­ters and I un­der­stand our drink­ing wa­ter comes out of the lake and the al­gae is block­ing the fil­ters for the town’s wa­ter sup­plies. That is one of the ma­jor things for Wanaka, it gets into the ir­ri­ga­tion pumps.’’

Otago Fish and Game op­er­a­tions man­ager Ian Had­land said lake snow was not a new is­sue with lake-users strug­gling with it in Wanaka, but it had not been preva­lent in Lake Wakatipu up un­til this point.

‘‘It is a rel­a­tively new phe­nom­e­non there and it is the worst we have seen it at both.’’

It had not been no­ticed in Lake Dun­stan but the Cromwell lake was at risk, he said.

An Otago Univer­sity aca­demic had been re­search­ing it.

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